The objective of this component project is to contribute to knowledge concerning communicative development in children with retardation being reared at home and compare their progress to that of typically-developing children using data from two methodologically identical longitudinal studies that observed the children's unstructured interactions with their families at home. Proposed is continued collection of follow-up data from the 11 children with Down syndrome, and its analysis for inclusion in a book summarizing the findings from the longitudinal study as a basis for recommendations to parents and practitioners. Follow-up visits are to be made once a year. The child's language is tape recorded and information up-dated by interviewing the parents. Language data is analyzed and merged with prior data to project the trajectory of each child's language development.